Maximin 4

A two-term model is proposed for hydrocarbon and N-containing pi-radicals which are in close contact with one another. The first term is attractive (due to partially occupied frontier pi-orbitals), and the second, repulsive (due to hard-core repulsion between close-lying atoms). This model is applied to dimers where intermolecular contacts are closer than <0.95 x the sum of the atomic van der Waals radii. The maximin principle is proposed. The maximin principle states that the lowest energy conformation maximizes overlap of the frontier orbitals while simultaneously minimizing intermolecular contacts. A Hückel Hamiltonian, the mu(2)-Hamiltonian, which contains the above attractive and repulsive terms, is applied. The interaction surfaces of two pi-hydrocarbon radical cations were calculated for the three systems known crystallographically to contain cations in close contact: naphthalene, fluoranthene, and pyrene. The global minima of these surfaces correspond to the experimentally determined structures. The mu(2)-Hamiltonian energy surfaces of the naphthalene cation dimer are qualitatively similar to those calculated at the RHF/6-311G(d,p) and MP2/6-311G(d,p) levels. The maximin principle is applied to N-containing pi-radicals. Except in the case of tetracyanoethene, the maximin principle correctly predicts the most common dimer crystal packing. (MgPc)(NO(3)).0.5THF and (MgPc)(ReO(4)).1.5THF (Pc = phthalocyanine) were prepared: both new crystal structures follow the maximin principle. The maximin principle is used to suggest the dimer cation ground state of oligoacenes, cations important as organic hole-based semiconductors.

Importance: The use of sacubitril/valsartan is not endorsed by practice guidelines for use in patients with New York Heart Association class IV heart failure with a reduced ejection fraction because of limited clinical experience in this population. Objective: To compare treatment with sacubitril/valsartan treatment with valsartan in patients with advanced heart failure and a reduced ejection fraction and recent New York Heart Association class IV symptoms. Design, setting, and participants: A double-blind randomized clinical trial was conducted; a total of 335 patients with advanced heart failure were included. The trial began on March 2, 2017, and was stopped early on March 23, 2020, owing to COVID-19 risk. Intervention: Patients were randomized to receive sacubitril/valsartan (target dose, 200 mg twice daily) or valsartan (target dose, 160 mg twice daily) in addition to recommended therapy. Main outcomes and measures: The area under the curve (AUC) for the ratio of N-terminal pro-brain natriuretic peptide (NT-proBNP) compared with baseline measured through 24 weeks of therapy. Results: Of the 335 patients included in the analysis, 245 were men (73%); mean (SD) age was 59.4 (13.5) years. Seventy-two eligible patients (18%) were not able to tolerate sacubitril/valsartan, 100 mg/d, during the short run-in period, and 49 patients (29%) discontinued sacubitril/valsartan during the 24 weeks of the trial. The median NT-proBNP AUC for the valsartan treatment arm (n = 168) was 1.19 (IQR, 0.91-1.64), whereas the AUC for the sacubitril/valsartan treatment arm (n = 167) was 1.08 (IQR, 0.75-1.60). The estimated ratio of change in the NT-proBNP AUC was 0.95 (95% CI 0.84-1.08; P = .45). Compared with valsartan, treatment with sacubitril/valsartan did not improve the clinical composite of number of days alive, out of hospital, and free from heart failure events. Aside from a statistically significant increase in non-life-threatening hyperkalemia in the sacubitril/valsartan arm (28 [17%] vs 15 [9%]; P = .04), there were no observed safety concerns. Conclusions and relevance: The findings of this trial showed that, in patients with chronic advanced heart failure with a reduced ejection fraction, there was no statistically significant difference between sacubitril/valsartan and valsartan with respect to reducing NT-proBNP levels. Trial registration: ClinicalTrials.gov Identifier: NCT02816736.

Maximin 3 is a 27-residue-long cationic antimicrobial peptide found in the skin secretion and brain of the Chinese red-belly toad Bombina maxima. The peptide is of biological interest as it possesses anti-HIV activity, not found in the other maximin peptides, in addition to antimicrobial, antitumor and spermicidal activities. The three-dimensional structure of maximin 3 was obtained in a 50/50% water/2,2,2-trifluoroethanol-d3 mixture using two-dimensional NMR spectroscopy. Maximin 3 was found to adopt an α-helical structure from residue G1 to A22, and a coil structure with a helical propensity in the C-terminal tail. The peptide is amphipathic, showing a clear separation between polar and hydrophobic residues. Interactions with sodium dodecyl sulfate micelles, a widely used bacterial membrane-mimicking environment, were modeled using molecular dynamics simulations. The peptide maintained an α-helical conformation, occasionally displaying a flexibility around residues G9 and G16, which is likely responsible for the peptide's low haemolytic activity. It is found to preferentially adopt a position parallel to the micellar surface, establishing a number of hydrophobic and electrostatic interactions with it.